1. Field of the Invention
This invention relates to a track roller having a roller, which rolls on a track of a cam mechanism or a linearly moving part, as an outer race in, for example, a loom and a transfer apparatus.
2. Description of the Prior Art
In a conventional loom and a conventional transfer apparatus, a roller having an outer race of a large thickness and rolling on a track of a cam mechanism or a linearly moving mechanism is known as a track roller. The track roller is generally in the shape of a disc, and provided with a thick-walled outer race, a thick-walled inner race and balls as rolling elements interposed between the inner and outer races. The inner race is fitted firmly around a mount member, and the outer race is supported rotatably on the inner race via the rolling elements.
The bearings for supporting the outer race of the track roller rotatably with respect to the inner race, i.e. the track roller bearings include a needle roller bearing, a cylindrical roller bearing and a ball bearing. In order to retain the rolling elements of the bearing rollably, a retainer is provided in some cases. In such a track roller, it is preferable that the bearing be provided with the largest possible number of rolling elements so as to transmit an impact imparted to the track roller between the inner and outer races. In order to load a bearing body with a plurality of rolling elements, a method of inserting the rolling elements thereinto via an insert hole formed in an outer circumferential wall of the outer race so that the insert hole extends, for example, in the radial direction thereof is conceivable.
Providing a rolling element insert hole in a bearing having opposed raceway grooves in the inner and outer races is disclosed in, for example, Japanese Utility Model Publication No. 16495/1987, Japanese Patent Laid-Open No. 247818/1989 and Japanese Utility Model Laid-Open No. 89580/1992.
The bearing disclosed in Japanese Utility Model Publication No. 16495/1987 is a cross roller bearing or a cross taper bearing in which rollers or conical rollers, which constitute rolling elements, are alternately provided. This bearing is provided with a roller insert hole in at least one portion of the outer or inner race, the inner diameter of the insert hole being set slightly larger than the diameter of rollers or the maximum diameter of conical rollers. The rollers or conical rollers inserted from this insert hole are fed into the 90.degree. V-shaped raceway groove of the inner race, inclined gradually from the axis of the insert hole in the lateral direction by a tool, and finally turned 45.degree. to left and right alternately with respect to the insert hole, whereby the rollers are set along the mentioned V-shaped groove. A cover which has the same shape as the insert hole and a V-shaped groove formed in an inner end surface thereof and continuous with the V-shaped groove of the inner or outer race, and which is used as a guide for the rolling elements is inserted into the insert hole. The inserted cover is fixed to the inner or outer race by a knock pin inserted thereinto from a side surface thereof.
The bearing disclosed in Japanese Patent Laid-Open No. 247818/1989 is provided in its race, which constitutes an inner or outer race, with a cylindrical roller insert hole of the smallest possible inner diameter which is between the diameter of the cylindrical rollers and the length of a diagonal of the raceway, in such a manner that, when the inserted cylindrical rollers contact the raceway surface on the inner side of the bearing they roll freely and are set properly on the raceway surface. The invention disclosed in this publication also relates to a thin-walled cross roller bearing provided with a recessed stepped portion between the inner surface of an insert hole-sealing cover and a raceway surface of a race. The thin-walled cross roller bearing is designed so as to prevent the formation of the insert hole from causing the strength of the race from lowering, prevent the occurrence of damage to the cover by avoiding the contacting of the cover and cylindrical rollers with each other, and prevent the rolling resistance of the rolling elements from increasing.
The bearing disclosed in Japanese Utility Model Laid-Open No. 89580/1992 relates to a roller lever for a cam machine which controls a held frame of a loom. In this roller lever, an outer race is supported on an inner race, which is fixed to a lever body, via rolling elements, which are inserted from a side portion of the inner race into a bearing body via a notch formed in the inner race, the notch being finally closed with a plug comprising an elastic body.
In this cross roller bearing, the radial thickness of the races including inner and outer races is not greatly large as compared with the size of the rolling elements to be loaded into a bearing body, and the outer circumferential surface of the outer race is not used as a rolling surface at which the bearing rolls on a track. Even when the outer race is provided as a rotary part, another rotary body is fitted there around, so that it is possible to form an insert hole so as to extend in the radial direction of the race, and load the rolling elements into the race through the insert hole.
In a track roller, however, both of the races, i.e. outer and inner races are formed to a large radial wall thickness and a small axial wall thickness, and the rolling element inserting structure applied to the above-described cross roller bearing cannot be applied as it is to the track roller. In order to provide an insert hole, which is similar to that in the cross roller bearing, in the track roller, a long insert hole extending from the outer circumferential surface of the outer race in the radial direction thereof is necessarily formed in the axially thin-walled outer race. Consequently, the thickness of the portion of the outer race which is left between the inner surface of the insert hole and the side surface of the outer race becomes small, and the strength necessary for the race cannot be secured. Since the insert hole becomes long, a rolling element loading operation including an operation for aligning the insert hole with a pocket of a retainer becomes difficult and takes a long time. The outer race of the track roller rolls on a track surface, such as a cam surface, and, therefore, the outer surface of the outer race has to be machined smooth surface. However, the insert hole is liable to cause a stepped portion to occur on the outer surface of the outer race.
In the roller lever for a cam machine, the plug with which to close the notch formed in the inner race is formed out of an elastically deformable material, for example, a resin material, so that it is difficult that the notch-carrying portion of the track which is elastically deformed supports a load. It is troublesome to grind or cut a notch of a certain shape, and, in such a case, the processing accuracy decreases. Since the plug closes the notch which can be seen from the outside, there is the possibility that the plug comes off when it contacts extraneous matter.